Age Range: 14 to 16

Case Study – Hurricane Igor (Sept 2010)

Post date 9 November 2020

A Met Office forecaster was working on secondment in Bermuda during
hurricane Igor. Some thoughts were gathered from somebody who experienced
it in person.

What is a hurricane?

A hurricane is a storm system which has a large low pressure centre. They produce heavy rain and have strong winds. To be classed as a hurricane the mean (as opposed to gust speeds) wind speeds must be in excess of 74 mph. The table below shows the Saffir-Simpson hurricane scale.

A hurricane with a wind speed of 74 mph is classed as a Category 1 hurricane. Category five hurricanes have wind speeds in excess of 155 mph. As well as heavy rain and intense wind hurricanes are traditionally accompanied by storm surges. Hurricanes form over warm tropical seas where the sea surface temperature is at least 27 °C. Moist air and converging winds are also required. Most hurricanes initially form to the west of Africa. As the hurricane develops it forms a clearly defined eye.

This satellite image shows Hurricane Igor.
The eye can clearly be seen as can the rain bands around it.

On 17 September Bermuda was placed under a hurricane watch. It was feared that Igor would affect Bermuda as a Category three. On the 20 September Igor passed roughly 40 miles to the west of Bermuda. Winds reached sustained of 91 mph with gusts of 117 mph, in actual fact a Category one hurricane.

The impacts on Bermuda

Every year the Atlantic hurricane season spans from the start of June to the end of November.

Why was Igor in particular chosen for this case study?

The reason is that Andy, a Met Office forecaster was on secondment with the Bermuda Weather Service and he experienced the full effects of the hurricane. It is good to get some thoughts from someone who experienced the effects in person.

“Hurricane Igor was predicted to be a direct hit on Bermuda. My job was to keep track of the forecasts and warnings for the Bermuda Weather Service, working closely with the National Hurricane Centre. This was exciting but the safety of the Islanders was always a concern. When the hurricane moved near, the noise in the weather centre became immense. The storm proof windows warped and there was a distinct smell of fish from the sea spray. Into the night there were flashes in the distance, which signalled the many downed power lines. Meanwhile reports came in of flooding in St Georges and some boats let loose from their moorings. When Igo finally cleared the Bermuda nobody was injured because they were prepared, thanks to the forecast and the action of government emergency agencies.”

The main impacts were due to the winds which downed trees and as a result the power supply to around 28,000 people was cut. The airport was closed for 2 days. Several boats were broken from their moorings and damaged on rocks.

No evacuation plans were initiated but a school was converted into a shelter for anyone who felt unsafe. A small number of emergency rescues had to be made but thankfully nobody was hurt.

The main causeway between St David’s and St George’s islands was damaged and one lane was closed for several days.

Tourists were more apprehensive about staying on the island with the majority choosing to leave Bermuda a week or so before Igor’s arrival. A Royal Navy vessel was positioned offshore to assist if required during the hurricane and also in the post-hurricane recovery effort.

The damage was estimated to be less than $500,000. Officials believe that the biggest financial impact of Bermuda was vastly reduced income from tourism. With so many tourists choosing to leave Bermuda (and many cancelling their trips to Bermuda) during the run-up to Igor this had a major impact on hotel and restaurant trade etc.

Web page reproduced with the kind permission of the Met Office

Case Study – Great Storm

Post date 9 November 2020

The Great Storm of 1987

A powerful storm ravaged many parts of the UK in the middle of October 1987.

With winds gusting at up to 100mph, there was massive devastation across the country and 18 people were killed. About 15 million trees were blown down. Many fell on to roads and railways, causing major transport delays. Others took down electricity and telephone lines, leaving thousands of homes without power for more than 24 hours.

Buildings were damaged by winds or falling trees. Numerous small boats were wrecked or blown away, with one ship at Dover being blown over and a Channel ferry was blown ashore near Folkestone. While the storm took a human toll, claiming 18 lives in England, it is thought many more may have been hurt if the storm had hit during the day.

The storm gathers

Warning the public

How the storm measured up

A hurricane or not?

The aftermath

The storm gathers

Four or five days before the storm struck, forecasters predicted severe weather was on the way. As they got closer, however, weather prediction models started to give a less clear picture. Instead of stormy weather over a considerable part of the UK, the models suggested severe weather would pass to the south of England – only skimming the south coast.

During the afternoon of 15 October, winds were very light over most parts of the UK and there was little to suggest what was to come. However, over the Bay of Biscay, a depression was developing. The first gale warnings for sea areas in the English Channel were issued at 6.30 a.m. on 15 October and were followed, four hours later, by warnings of severe gales.

At 12 p.m. (midday) on 15 October, the depression that originated in the Bay of Biscay was centred near 46° N, 9° W and its depth was 970 mb. By 6 p.m., it had moved north-east to about 47° N, 6° W, and deepened to 964 mb.

At 10.35 p.m. winds of Force 10 were forecast. By midnight, the depression was over the western English Channel, and its central pressure was 953 mb. At 1.35 a.m. on 16 October, warnings of Force 11 were issued. The depression moved rapidly north-east, filling a little as it went, reaching the Humber estuary at about 5.30 am, by which time its central pressure was 959 mb. Dramatic increases in temperature were associated with the passage of the storm’s warm front.

Warning the public

During the evening of 15 October, radio and TV forecasts mentioned strong winds but indicated heavy rain would be the main feature, rather than strong wind. By the time most people went to bed, exceptionally strong winds hadn’t been mentioned in national radio and TV weather broadcasts. Warnings of severe weather had been issued, however, to various agencies and emergency authorities, including the London Fire Brigade. Perhaps the most important warning was issued by the Met Office to the Ministry of Defence at 0135 UTC, 16 October. It warned that the anticipated consequences of the storm were such that civil authorities might need to call on assistance from the military.

In south-east England, where the greatest damage occurred, gusts of 70 knots or more were recorded continually for three or four consecutive hours. During this time, the wind veered from southerly to south-westerly. To the north-west of this region, there were two maxima in gust speeds, separated by a period of lower wind speeds. During the first period, the wind direction was southerly. During the latter, it was south-westerly. Damage patterns in south-east England suggested that whirlwinds accompanied the storm. Local variations in the nature and extent of destruction were considerable.

How the storm measured up

Fig. 1 shows maximum gusts (in knots) during the storm.

Comparisons of the October 1987 storm with previous severe storms were inevitable. Even the oldest residents of the worst affected areas couldn’t recall winds so strong, or destruction on so great a scale.

The highest wind speed reported was an estimated 119 knots (61 m/s) in a gust soon after midnight at Quimper coastguard station on the coast of Brittany (48° 02′ N 4° 44′ W).
The highest measured wind speed was a gust of 117 knots (60 m/s) at 12.30 am at Pointe du Roc (48° 51′ N, 1° 37′ W) near Granville, Normandy.
The strongest gust over the UK was 100 knots at Shoreham on the Sussex coast at 3.10 am, and gusts of more than 90 knots were recorded at several other coastal locations.
Even well inland, gusts exceeded 80 knots. The London Weather Centre recorded 82 knots at 2.50 am, and 86 knots was recorded at Gatwick Airport at 4.30 am (the authorities closed the airport).

A hurricane or not?

TV weather presenter Michael Fish will long be remembered for telling viewers there would be no hurricane on the evening before the storm struck. He was unlucky, however, as he was talking about a different storm system over the western part of the North Atlantic Ocean that day. This storm, he said, would not reach the British Isles — and it didn’t. It was the rapidly deepening depression from the Bay of Biscay which struck.
This storm wasn’t officially a hurricane as it did not originate in the tropics — but it was certainly exceptional. In the Beaufort scale of wind force, Hurricane Force (Force 12) is defined as a wind of 64 knots or more, sustained over a period of at least 10 minutes. Gusts, which are comparatively short-lived (but cause a lot of destruction) are not taken into account. By this definition, Hurricane Force winds occurred locally but were not widespread.

The highest hourly-mean speed recorded in the UK was 75 knots, at the Royal Sovereign Lighthouse. Winds reached Force 11 (56–63 knots) in many coastal regions of south-east England. Inland, however, their strength was considerably less. At the London Weather Centre, for example, the mean wind speed did not exceed 44 knots (Force 9). At Gatwick Airport, it never exceeded 34 knots (Force 8).

The powerful winds experienced in the south of England during this storm are deemed a once in 200 year event — meaning they were so unusually strong you could only expect this to happen every two centuries. This storm was compared with one in 1703, also known as a ‘great storm’, and this could be justified. The storm of 1987 was remarkable for its ferocity, and affected much the same area of the UK as its 1703 counterpart.

Northern Scotland is much closer to the main storm tracks of the Atlantic than south-east England. Storms as severe as October 1987 can be expected there far more frequently than once in 200 years. Over the Hebrides, Orkney and Shetland, winds as strong as those which blew across south-east England in October 1987 can be expected once every 30 to 40 years.

The 1987 storm was also remarkable for the temperature changes that accompanied it. In a five-hour period, increases of more than 6 °C per hour were recorded at many places south of a line from Dorset to Norfolk.

The aftermath

Media reports accused the Met Office of failing to forecast the storm correctly. Repeatedly, they returned to the statement by Michael Fish that there would be no hurricane — which there hadn’t been. It did not matter that the Met Office forecasters had, for several days before the storm, been warning of severe weather. The Met Office had performed no worse than any other European forecasters when faced with this exceptional weather event.

However, good was to come of this situation. Based on the findings of an internal Met Office enquiry, scrutinised by two independent assessors, various improvements were made. For example, observational coverage of the atmosphere over the ocean to the south and west of the UK was improved by increasing the quality and quantity of observations from ships, aircraft, buoys and satellites, while refinements were made to the computer models used in forecasting.

Strength of gusts

Fig 1. Graphic showing areas with strengths of maximum gusts.

Web page reproduced with the kind permission of the Met Office

Other MetLink resources linked to the 1987 storm:

Weather articles:

Damage to trees and woodlands in the storm of 15-16 October 1987, Quine, 1988
The Storm of 15-16 October 1987: A personal experience, H.D.Lawes, 1988
The Great Storm of 1987, Burt & Mansfield, 1988
The storm, the Media and the Enquiry, J. Houghton, 1988

Case Study – Floods

Post date 9 November 2020

Floods and flooding

Floods can be devastating — costing the lives of people and animals, as well as destroying crops, homes and businesses.

The east coast of England and the Netherlands have always been prone to flooding as storms track off the North Sea, bringing water surges and huge waves with them.

The devastation floods can cause

Flooding caused by surges

The surge of 1953

Storm tide warnings

What happened to cause this storm?

Surges still causing damage

Flood defences

The devastation floods can cause

About 10,000 people died in a single flood in the Netherlands in 1421. Water from the North Sea flooded inland and swept through 72 villages, leaving a trail of destruction.

Further severe floods struck the region in 1570, 1825, 1894, 1916 and 1953. All of them occurred despite the area having extensive flood defence systems — sometimes nature’s power is just too strong. These defences are vital for the Netherlands, where 40% of the country is below sea level.

Along the coast of eastern England there have also been many failures of coastal defences. Even London has seen disastrous flooding. In January 1928 a northerly gale raised water levels in the Thames Estuary. Water overtopped embankments and low-lying riverside districts were flooded in the city, drowning 14 people.

Flooding caused by surges

Tides affect sea levels, but sometimes the weather will also play its part in raising or lowering water height. This is called a surge and is measured by how much higher or lower the sea is than expected on any given tide. A surge is positive if the water level is higher than the expected tide, and negative if lower. Positive surges happen when water is driven towards a coast by wind and negative when it is driven away.

While wind is the main cause of surges, barometric pressure – the pressure in the air — also plays its part. When pressure decreases by one millibar, sea level rises by one centimetre. Therefore, a deep depression with a central pressure of about 960 mb causes sea level to rise half a metre above the level it would have been had pressure been about average (1013 mb). When pressure is above average, sea level correspondingly falls.

When strong winds combine with very low pressure they can raise the sea level in eastern England by more than two metres. Fortunately such surges normally occur at mid-tide levels — so do not cause as much damage. If they were to coincide with high tide it could be a very different story.

Surges travel counter-clockwise around the North Sea — first southwards down the western half of the sea, then northwards up the western side. They take about 24 hours to progress most of the way around.

Waves, generated by strong winds, are another flooding factor. While coastal defences are designed to deal with high tides, these defences can be badly damaged by a pounding from large and powerful waves. Some waves are so large that they simply break over coastal defences, sending water flooding in and undermining sea-wall foundations until they collapse.

The surge of 1953

More than 2,000 people drowned at the end of January 1953 when the greatest surge on record, happened in the North Sea. The surge measured nearly three metres in Norfolk and even more in the Netherlands. About 100,000 hectares of eastern England were flooded and 307 people died. A further 200,000 hectares were flooded in the Netherlands, and 1,800 people drowned.

The storm that caused this disastrous surge was among the worst the UK had experienced.

Hurricane force winds blew down more trees in Scotland than were normally felled in a year.
A car ferry, the Princess Victoria, sank with the loss of 133 lives — but 41 of the passengers and crew survived.
From Yorkshire to the Thames Estuary, coastal defences were pounded by the sea and gave way under the onslaught.

As darkness fell on 31 January, coastal areas of Lincolnshire bore the brunt of the storm.

Sand was scoured from beaches and sand hills
Timber-piled dunes were breached
Concrete sea walls crumbled
The promenades of Mablethorpe and Sutton-on-Sea were wrecked.
Salt water from the North Sea flooded agricultural land

Later that evening, embankments around The Wash were overtopped and people drowned in northern Norfolk. At Wells-next-the-Sea, a 160-ton vessel was left washed up on the quay after waves pounded it ashore.

In 1953, because many telephone lines in Lincolnshire and Norfolk were brought down by the wind, virtually no warnings of the storm’s severity were passed to counties farther south until it was too late. Suffolk and Essex suffered most.

By midnight, Felixstowe, Harwich and Maldon had been flooded, with much loss of life. Soon after midnight, the sea walls on Canvey Island collapsed and 58 people died. At Jaywick in Clacton, the sea rose a metre in 15 minutes and 35 people drowned.

The surge travelled on. From Tilbury to London’s docklands, oil refineries, factories, cement works, gasworks and electricity generating stations were flooded and brought to a standstill.

In London’s East End, 100 metres of sea wall collapsed, causing more than 1,000 houses to be inundated and 640,000 cubic metres of Thames water to flow into the streets of West Ham. The BP oil refinery on the Isle of Grain was flooded, and so was the Naval Dockyard at Sheerness.

Storm tide warnings

The disastrous surge of 1953 was predicted successfully by the Met Office and the Dutch Surge Warning Service. Forecasts of dangerously high water levels were issued several hours before they happened. An inquiry into the disaster recommended, however, that a flood warning organisation should be set up. This led to the setting up of the Storm Tide Warning Service.

What happened to cause this storm?

In the early hours of 30 January 1953, the storm that was to cause the havoc was a normal looking depression with a central pressure of 996 mb, located a little to the south of Iceland. While it looked normal, during the day the pressure rapidly deepened and headed eastwards.

By 6 p.m. on 30 January, it was near the Faeroes, its central pressure 980 mb. By 12p.m. (midday) on 31 January, it was centred over the North Sea between Aberdeenshire and southern Norway and its central pressure was 968 mb.

Meanwhile, a strong ridge of high pressure had built up over the Atlantic Ocean south of Iceland, the pressure within being more than 1030 mb. In the steep pressure gradient that now existed on the western flanks of the depression, there was a very strong flow from a northerly point. Winds of Force 10 were reported from exposed parts of Scotland and northern England. The depression turned south-east and deepened to 966 mb before filling. By midday on 1 February, it lay over northern Germany, its central pressure 984 mb.

All day on 31 January, Force 10/11 winds blew from the north over western parts of the North Sea. They drove water south, and generated waves more than eight metres high. The surge originated in the waters off the north-east coast of Scotland and was amplified as it travelled first southwards along the eastern coasts of Scotland and England, and then north-east along the coast of the Netherlands. It reached Ijmuiden in the Netherlands around 4 a.m. on 1 February.

Surges still causing damage

Since 1953, there have been other large surges in the North Sea. Among them one, on 12 January 1978, caused extensive flooding and damage along the east coast of England from Humberside to Kent. London came close to disaster, escaping flooding by only 0.5 m, and the enormous steel and rubber floodgates designed to protect the major London docks were closed for the first time since their completion in 1972.

Flood defences

Concern over rising sea levels, and the potential catastrophe if London were to be flooded, led the Government to build the Thames Flood Barrier. Based at Woolwich and finished in 1982, it is the world’s second largest movable flood barrier. It is designed to allow ships to pass in normal times, but flood gates come down to stop storm surges in times of need. The barriers are closed about four times a year, on average.

Over the years, coastal defences in the Netherlands and eastern England have been raised and strengthened continually to protect against storm surges. Our coasts and estuaries are safer now than they have ever been. Nevertheless, surges remain a threat, as complete protection against the most extreme can never be guaranteed.

The likelihood of being taken by surprise is now lower, because weather and surge forecasting systems have improved greatly in recent years, and the Storm Tide Forecasting Service has established clear and effective procedures for alerting the authorities when danger threatens.

Web page reproduced with the kind permission of the Met Office

Case Study – Boscastle Floods

Post date 9 November 2020

boscastle flooding — Aerial photo of the flood waters gushing through Boscastle (courtesy of Apex News &∓ Pictures)

Floods Devastate Village

On 16 August 2004, a devastating flood swept through the small Cornish village of Boscastle.

Very heavy rain fell in storms close to the village, causing two rivers to burst their banks. About two billion litres of water then rushed down the valley straight into Boscastle.

Residents had little time to react. Cars were swept out to sea, buildings were badly damaged and people had to act quickly to survive. Fortunately, nobody died – thanks largely to a huge rescue operation involving helicopters — but there was millions of pounds worth of damage.

Physical Impacts

Responses to the flooding

What happened to cause this event?

Physical Impacts

Flooding
On the day of the flood, about 75mm of rain fell in two hours — the same amount that normally falls in the whole of August. Huge amounts of water from this sudden downpour flowed into two rivers, the Valency and Jordan (which flows into the Valency just above Boscastle). Both overflowed, and this caused a sudden rush of water to speed down the Valency — which runs through the middle of Boscastle.

Destruction of houses, businesses and gardens
Floodwater gushed into houses, shops and pubs. Cars, walls and even bridges were washed away. The church was filled with six feet of mud and water. Trees were uprooted and swept into peoples’ gardens. The weight of water eroded river banks, damaged gardens and pavements.

Human Impacts
There was a huge financial cost to the floods. This included:

the rescue operation – involving helicopters, lifeboats, and the fire service.
the loss of 50 cars
damage to homes, businesses and land
a loss of tourism, a major source of income for the area

The flooding also had several other key impacts on Boscastle and its inhabitants. These included:

environmental damage to local wildlife habitats
coastal pollution caused as debris and fuel from cars flowed out to sea.
long-term disruption to the village, as a major rebuild project had to be carried out.
long-term stress and anxiety to people traumatised by the incident.

Responses to the flooding

John Prescott, the Deputy Prime Minister, and Prince Charles visited members of the emergency services and the local GP surgery, which acted as the emergency centre, in the days following the disaster.
Prince Charles, who is the Duke of Cornwall, made a large donation to a fund to help rebuild parts of Boscastle.
The Environment Agency is responsible for warning people about floods and reducing the likelihood of future floods. The Environment Agency has carried a major project to increase flood defences in Boscastle, with the aim of preventing a similar flood happening again.
We are investing in new ways of predicting heavy rainfall events on a small scale to produce better warnings.

In Pictures

What happened to cause this event?

Weather map Fig. 1 shows the weather map for midday on 16 August. The wind is blowing anticlockwise about the low pressure area, so the air is arriving into Boscastle from a south-westerly direction. It is a warm and moist tropical maritime air mass. The line labelled (known as a trough line) caused very heavy rain and thunderstorms. A trough is an area of localised rain and thunderstorms. A line of convergence formed near the coast line, where air moving in almost opposite directions collides, this helped to increase the rate of ascent and produced very heavy rain. There is more about surface pressure charts in the weather section of the Met Office website.

Weather chart

Radar imagery

Fig. 2 shows radar pictures at 12 p.m. (midday) on 16 August.

The rainfall rate key shows how the colours in the image relate to the rate the rainfall is falling. For example, the red areas indicate that rain is falling at between eight and 16 mm per hour.

A line of very heavy rain starts at about 1 p.m. on the moors close to Boscastle. It remains over the area for about six hours. Rainfall rates of at least 32 mm per hour are being measured.

There is more about rainfall radar in the weather section of the Met Office website.

Satellite imagery
Fig. 3 shows an animation of satellite pictures from 12 p.m. (midday) to 7 p.m. on 16 August.

The thickest cloud is shown by the brightest white areas on the picture. The pictures show cloud forming over Boscastle at about 1 p.m. and staying there for much of the afternoon.

Further information on other websites
BBC News website covering the Boscastle flooding
BBC News article – Boscastle one year on

Boscastle 16 August 2004 the day of the flood, 2006, Galvin, 61, 29

Web page reproduced with the kind permission of the Met Office

Case Study – Bodmin Snow

Post date 9 November 2020

A snowy day in Winter 2005

Heavy snow stops traffic on main route through Cornwall.

More than 1,000 people were left stranded in their vehicles on one of the busiest roads in Cornwall because of heavy snowfall. On Friday 25 November 2005 hundreds of cars became stuck on the A30 over Bodmin Moor after the slippery conditions caused a crash involving several cars. Helicopters and all-terrain vehicles were brought in to rescue the stranded motorists, taking them to emergency accommodation in nearby leisure centres for the night.

Many children also got stuck in their schools for several hours, as the snow meant they could not leave and parents could not come to collect them. Almost 70 of Cornwall’s 273 schools were closed.

Impacts
What happened to cause this weather?

Impacts

Health and wellbeing
Despite the terrible conditions and many crashes, the only injuries to people involved a fire engine, which came off the A30 on the way to answer an emergency call. One firefighter was taken to hospital by helicopter with serious, but not life-threatening, injuries.

Disruption to transport

Map showing the area in Cornwall affected by the snow

A30 closed with gridlocked traffic. Railway services were affected. Fallen trees on one of the railway lines from London to Penzance caused trains to be delayed.

People stranded at home/on the road/at school
About 2,000 school pupils were stuck in schools and their teachers had to look after them. Some school children were forced to stay at homes of teachers and friends, and in hotels. A number of weather-sensitive outdoor events and some indoor events, such as pony show-jumping competitions, were cancelled on Saturday 26 November.

Financial effects on local economy
Likely to have ran into several hundreds of thousands, or even millions, of pounds. There was the cost of carrying out rescue operations and setting up of emergency shelters. The impact of people not attending work and goods not being delivered to businesses is likely to have added to the cost of the incident.

What happened to cause this weather?

Snow
Snow is a frozen type of precipitation. Precipitation also includes rain, hail, sleet, fog etc. Snow normally occurs when precipitation occurs and the air temperature at ground level is below 2 °C. Snow is most common in the UK in the winter months. The snow which affected the south-west of England on 25 November was an unusual occurrence in November, as it an autumn month.

Snow depths tend to only be measured once per day at 9 a.m. It is likely that at the height of the event snow depths were greater, but this may have melted overnight. There may also be other locations, where there are no weather stations, which had greater depths of snow.

Weather chart
Snow can occur when air reaches us from a northerly or easterly direction, this helps to define the air mass.

Fig. 1 shows the weather chart at midday on Friday 25 November. The blue arrows show air has moved down from the Arctic to reach south-west England. This air is flowing anticlockwise around the area of low, so the wind direction over the south-west of England is a northerly.

The air mass type is Arctic Maritime. This is cold and moist air which often has periods of snow. The little cold front over south-west England, shown by a line with triangles, indicates where the snow is long-lasting and heaviest. There is more about surface pressure charts in the weather section of the Met Office website.

Satellite imagery
Fig. 2 is an animation visible satellite images from 1 p.m. to 5 p.m. on Friday 25 November.

The brightest white areas show where the thickest cloud is and where snowfall is most likely to be falling. The thickest cloud occurs over Bodmin Moor at around 2 p.m. and 3 p.m.

The satellite is sensing how much sunlight is being reflected from the cloud. The darkening of the last image is about the time of sunset at 5 p.m. The dark areas of the picture over Exeter at 3 p.m. and 4 p.m. show where the cloud has cleared.

Weather chart

Satellite imagery

Radar imagery
Fig. 3 is a animation of the radar imagery from 11 a.m. to 6 p.m. on Friday 25 November. The legend, or key, shows the water equivalent in millimetres (mm) per hour. 1 mm of water is about the same as a 10 mm deep snowfall.

The radar imagery suggests the band of snow is moving westwards. It shows that it snowed for most of the day over Bodmin Moor before stopping around 6 p.m. It also suggests some high rates of snowfall at times, shown by the pink colours, e.g. 8.0-12.0 mm per hour.

Air temperatures
The temperature remained below 1 °C for the whole of this period on Bodmin Moor, and over much of the surrounding area. When the precipitation occurred, it did fall as snow and, because the roads were so cold, it was easy for it to settle on the A30 road surface.

Radar imagery

Web page reproduced with the kind permission of the Met Office

Case Studies

Post date 9 November 2020

More case studies can be found on the Met Office website and here.

IPCC Updates for Geography Teachers

Post date 9 November 2020

Climate Change Updates

Evidence from the 2013 Intergovernmental Panel on Climate Change (IPCC) Report: for Geography Teachers

Factsheets:

1. Signs of a Changing Climate
2. Past Changes in Northern Hemisphere Temperature
3. Causes of Recent Changes in Global Surface Temperature
4. The Earth’s Energy Balance
5. Changes to the Global Atmospheric Circulation
6. Impacts of Climate Change Already Observed
7. Sea level and marine ecosystems
8. Extreme Weather Hazards
9. The Impact of Climate Change on Food Production
10. The Impact of Climate Change on Security

Glossary

UK National Curriculum Links

Download complete booklet

All the figures and Frequently Asked Questions referenced in this booklet may be downloaded from the IPCC website or www.metlink.org

IPCC, 2013: Climate Change 2013: The Physical Science Basis. Working Group I Contribution to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

IPCC, 2014: Climate Change 2014: Impacts, Adaptation and Vulnerability. Working Group II Contribution to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

IPCC, 2014: Climate Change 2014: Mitigation of Climate Change. Working Group III Contribution to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

The Intergovernmental Panel on Climate Change (IPCC) is the leading international body for the assessment of climate change. It was established by the United Nations Environment Programme (UNEP) and the World Meteorological Organization (WMO) in 1988 to provide the world with a clear scientific view on the current state of knowledge in climate change and its potential environmental and socio-economic impacts. It reviews and assesses the most recent scientific, technical and socio-economic information produced worldwide relevant to the understanding of climate change.

1) Signs of a Changing Climate

What is the key evidence for climate change?

Evidence for a warming world comes from many independent indicators, from high up in the atmosphere to the depths of the oceans. They include increases in surface, atmospheric and oceanic temperatures; shrinking of glaciers; decreasing snow cover and sea ice; rising sea level and increasing atmospheric water vapour. Put together, we see that the evidence points unequivocally to one thing: the world has warmed since the late 19th century.

A rise in global average surface temperatures is the best-known indicator of climate change. Although each year and even decade is not always warmer than the last, global surface temperatures have warmed substantially since 1900.

Why is the cryosphere so important?

The cryosphere plays a major role in the Earth’s climate system. It has an impact on the water cycle, primary productivity, the surface energy budget, surface gas exchange and sea level and is therefore a fundamental control on the environment over a large part of the Earth’s surface. The cryosphere is sensitive to changing temperatures and provides some of the most visible signatures of climate change over time.

What evidence does the cryosphere reveal?

	Average Rate of ice loss during 1992-2001 (Gt per year)	Average Rate of ice loss year during 2002-2011 (Gt per year)
Greenland Ice Sheet	34	215
Antarctic Ice Sheet	30	147

Gt = Gigatonnes

The annual Arctic sea ice extent decreased over the period 1979–2012 by between 3.5 and 4.1% per decade. The extent has decreased in every season, and is most rapid in summer and autumn.
In total, all the glaciers in the world, excluding those on the periphery of ice sheets, lost approximately 226 Gt/ year in the period 1971–2009, approximately 275 Gt/ year in the period 1993–2009, and approximately 301 Gt/ year between 2005 and 2009.
Between 2003 and 2009, most of the glacier ice lost was from Alaska, the Canadian Arctic, the periphery of the Greenland ice sheet, the Southern Andes and the Asian Mountains.

IPCC links

This is FAQ 2.1 Figure 1 from the WG1 report for the 2013 IPCC 5AR.

WG1 FAQ2.1 Figure 2 shows several indicators of climate change over the past 150 years.

WG1 FAQ2.1 How do we know the world has warmed?

WG1 FAQ4.1 How is sea ice changing in the Arctic and Antarctic?

WG1 FAQ4.2 Are glaciers in mountain regions disappearing?

2) Past Changes in Northern Hemisphere Temperature

Is recent climate change similar to anything that has happened in the past?

Many studies have confidently indicated that the mean Northern Hemisphere temperature of the last 30 years exceeded any previous 30- year average during the past 1400 years. The studies are based on proxy data (indirect measures of the climate) including tree ring widths, stalactites and stalagmites, glaciers, bore hole data and marine and lake sediments.

New reconstructions of paleoclimates differ on precisely when and where the warmer and colder conditions occurred, including which seasons were particularly warm or cool. There is agreement that there were mostly warmer conditions from about 950 to 1250 AD (Medieval Climate Anomaly) and cooler conditions from about 1400 to 1850 AD (Little Ice Age). The IPCC concluded that although some decades during the MCA were in some regions as warm as in the late 20^th century, these warm periods did not occur as coherently across regions as the warming in the late 20th century.

What is Forcing?

Forcing represents any factor that influences global climate by heating or cooling the planet. Examples of forcings are volcanic eruptions, solar variations and anthropogenic (human) changes to the composition of the atmosphere.

Taking a longer term perspective shows the substantial role played by anthropogenic and natural forcings in driving climate variability on hemispheric scales prior to the twentieth century. It is very unlikely that Northern Hemisphere temperature variations from 1400 to 1850 can be explained by natural internal variability alone; – something, such as changes in solar and/ or volcanic activity, must have driven the changes.

Tropical sea-surface temperature from 3.5 Ma (Million years ago) to present. This figure shows that there was a slow cooling of climate over the last 3 million years as polar ice sheets grew partly in response to continental drift. At the Mid-Pleistocene Transition around 1.2 million to 700,000 years ago, the Milankovitch cycles started interacting differently with a shift to a dominant 100,000 year climate signal.

IPCC links

These are figures 5.2 and 5.8 from the WG1 report for the 2013 IPCC 5AR.

WG1 Figure 5.3 shows the Milankovitch cycles over the last 800,000 years together with atmospheric CO₂ content, sea level and tropical/ Antarctic temperatures.

WG1 Figure 5.7 shows individual reconstructions from different data sources.

From IPCC AR4:

FAQ 6.1 What Caused the Ice Ages and Other Important Climate Changes Before the Industrial Era?

Box 6.1: Orbital Forcing

Box TS.6 Orbital Forcing

3) Causes of Recent Changes in Global Surface Temperature

Global surface temperatures from 1870 to 2010, (a) The black line shows global surface temperatures (1870–2010) relative to the 1961-1990 average. The red line shows climate model simulations of global surface temperature change produced using the sum of the impacts on temperature from natural (b, c, d) and anthropogenic factors (e). Note the different vertical scales.

The IPCC concluded that “It is extremely likely that human activities caused more than half of the observed increase in global mean surface temperature from 1951 to 2010” (0.08 to 0.14 °C per decade). Over this time period:

Greenhouse gases contributed a global mean surface warming between 0.5°C and 1.3°C
Other anthropogenic forcings (such as land use changes and other atmospheric pollution) contributed between -0.6°C and 0.1°C,
Natural forcings (such as changes in the sun and in volcanic eruptions) contributed between -0.1°C and 0.1°C
Internal variability, due to naturally variable processes within the climate system such as the El Niño-Southern Oscillation, contributed between -0.1°C and 0.1°C.

The observed global mean surface temperature increase has slowed over the past 15 years compared to the past 30 to 60 years with the trend over 1998–2012 estimated to be around one third to one half of the trend over 1951–2012. This ‘hiatus’ is probably due to the cooling influences from natural radiative forcings (more volcanic eruptions and reducing output from the sun as part of the natural 11-year solar cycle) and internal variability (fluctuations within the oceans unrelated to forcings). Even with this ‘hiatus’ in the surface temperature warming trend, 2000-2010 has been the warmest decade in the instrumental record, which began in the mid 19^th century. The climate system has continued to accumulate energy, for example energy accumulation in the oceans has caused the global mean sea level to continue rising.

IPCC links

This is FAQ5.1 Figure 1 from the WG1 report for the 2013 IPCC 5AR.

WG1 Figure 8.11 Total solar irradiance since 1745

WG1 Figure 8.13 Measurements of 28 Years of volcanic aerosol in the stratosphere

WG1 Figure 10.5 shows the likely ranges for attributable warming trends over the 1951-2010 period due to greenhouse gases, other anthropogenic forcings (land use changes, other pollutants), natural forcings (solar and volcanic changes) and natural variability compared to observations.

WG1 FAQ 10.1 Climate is always changing. How do we determine the causes of observed changes?

4) The Earth’s Energy Balance

The Global annual average flows of energy under present day climate conditions. The numbers show the individual energy fluxes in W/m² and their range of uncertainty (in brackets). The net downward flow of sunlight at the top of Earth’s atmosphere (340 W/m² incoming minus 100 W/m² which is reflected back to space) is approximately balanced by the infra-red (heat) emissions to space (239 W/m²).

Since the last IPCC report, knowledge of the magnitude of the energy flows in the climate system has improved as new space-borne instruments have supplied data measuring the energy exchanges between the Sun, Earth and Space.

It is harder to measure the energy budget at the surface than at the top of the atmosphere because they cannot be directly measured by passive satellite sensors and surface measurements aren’t equally distributed across the earth’s surface. New estimates for the downward flow of heat at the surface have been established which include information on cloud base heights.

The amount of the Sun’s energy reaching the surface changed after 1950, with

a) decreases (‘dimming’) until the 1980s, because atmospheric pollutants (aerosols) make the atmosphere more reflective and also clouds, by increasing the number of water droplets in the clouds, which in turn increases the amount of sunlight reflected, and subsequent

b) increases (‘brightening’) as national and international legislation in the 1980s reduced the amount of pollutants in the atmosphere which increased the amount of energy reaching the surface.

How do human activities affect the Earths energy budget?

Human activities are continuing to affect the Earth’s energy budget by changing the emissions and resulting atmospheric concentrations of important greenhouse gases and aerosols and by changing land surface properties. The result of this is that the sum of the energy leaving the top of the atmosphere is less (239 + 100 W/m² than the energy entering it (340 W/m²). Most of this excess energy is absorbed at the surface, as shown by the orange box, causing the observed increase in temperatures in the lower atmosphere and oceans.

IPCC links

This is figure 2.11 from the WG1 report of the 2013 IPCC 5AR.

WG1 Figure 8.11 shows reconstructions of total solar irradiance since 1745.

WG1 Figure 8.13 shows the amount of aerosol in the stratosphere from volcanoes in the period 1984-2012.

WG1 FAQ 5.1 Is the Sun a major driver of recent changes in climate?

WG1 FAQ 7.1 How do clouds affect climate and climate change?

WG1 FAQ 7.2 How do aerosols affect climate and climate change?

WG1 FAQ 10.1 Climate is always changing. How do we determine the causes of observed changes?

WG1 FAQ 11.2 How do volcanic eruptions affect climate and our ability to predict climate?

AR4 WG1 FAQ1.3 What is the Greenhouse Effect? With FAQ 1.3 Figure 1

5) Changes to the Global Atmospheric Circulation

Robust cloud responses to greenhouse warming. No mechanisms contribute a robust negative feedback (reducing the size of the warming). Changes include rising high cloud tops and melting level, and increased polar cloud; broadening of the Hadley Cell and poleward migration of storm tracks, and narrowing of rainfall zones such as the Intertropical Convergence Zone (ITCZ).

Over the mid-latitude land areas of the Northern Hemisphere, precipitation has increased since 1901 (medium confidence before 1951 and high confidence after).

How might precipitation change?

Tropical oceanic rainfall is likely to increase with warmer oceans, particularly in the equatorial Pacific. As the ascending air associated with tropical rainfall drives the Hadley Cell, increasing tropical rainfall may intensify and broaden (poleward) the subtropical and mid-latitude dry zones that exist at the Hadley Cell’s outer edges, reducing rainfall there and expanding deserts.
In wetter mid-latitude regions and in high latitudes, average precipitation will likely increase, due to the poleward shift in the storm tracks and a greater atmospheric capacity for moisture at warmer temperatures. This increased moisture capacity will probably also produce more intense and frequent extreme precipitation events over most mid-latitude land masses and wet tropical regions.

How does cloud height affect climate?

In general, high clouds cool the climate during the day, by reflecting the Sun’s light, but warm it during the day and night by trapping heat lost from the Earth’s surface – the net effect is one of warming. Low clouds, on the other hand, mainly cool the climate, so if there are more extensive low clouds, this cooling effect would become larger.

What is the outlook?

In a warmer climate, high clouds are expected to rise in altitude and thereby exert a stronger greenhouse effect.
Jet streams and storm tracks shift poleward, in part due to the tropical troposphere warming by more than the mid-latitude troposphere; the temperature difference between these two regions controls the location and speed of the jet stream. The shift in jet stream will dry the subtropics and moisten the high latitudes. In turn, this causes further positive (amplifying) feedback (i.e. enhancing the greenhouse effect) via a net shift of cloud cover to the higher latitudes, thereby allowing more sun light in at low latitudes, where the suns light is more concentrated, to warm the surface.
Low cloud amount will decrease, especially in the subtropics, according to most climate models.

The most likely combined effect of changes to all cloud types is to amplify the surface temperature warming (a positive feedback).

IPCC links

This is Figure 7.11 from the WG1 report for the 2013 IPCC 5AR.

WG1 FAQ 7.1 How Do Clouds Affect Climate and Climate Change?

6) Impacts of Climate Change Already Observed

Global patterns of impacts in recent decades attributed to climate change (natural and anthropogenic).

Systems: In recent decades, changes in climate (including both anthropogenic and natural changes) have caused impacts on natural and human systems on all continents and oceans. The evidence of impacts is greatest for natural systems. Some impacts on human systems have also been attributed to climate change.

Terrestrial, freshwater, and marine species: Many have shifted their geographic ranges, seasonal activities, migration patterns, abundances, and species interactions in response to ongoing climate change. In the oceans, the distribution of phytoplankton and zooplankton has changed most. While only a few recent species extinctions have been attributed to climate change, natural global climate change at rates slower than current anthropogenic climate change caused significant ecosystem shifts and species extinctions in the past millions of years.

Water: In many regions, changing precipitation or melting snow and ice are altering hydrological systems, affecting water resources in terms of quantity and quality. Glaciers continue to shrink almost worldwide due to climate change, affecting runoff and water resources downstream. Climate change is causing permafrost warming and thawing in high-latitude regions and in mountainous regions.

IPCC links

This is Figure SPM Figure 2a from the WGII report for the 2014 IPCC 5AR.

It contains information taken from WGII SPM.2 table 1 key, Asia, Africa, Australasia, Central and South America, Europe, North America, Oceans, Polar Regions, Small Islands

WG1 FAQ 4.1 How is sea ice changing in the Arctic and Antarctic?

WG1 FAQ 4.2 Are glaciers in mountain regions disappearing?

WGII FAQ 3.1 How will climate change affect the frequency and severity of floods and droughts?

WGII FAQ 3.4 Does climate change imply only bad news about water resources?

WGII FAQ 4.4 How does climate change contribute to species extinction?

7) Sea level and marine ecosystems

Computer model simulations of the change in sea level relative to 1986-2005 for the period 2005-2100.

Sea Level

Global mean sea level is measured using tide gauge records and also, since 1993, satellite data.

Between 1901-2010, it has risen 0.19m at an average rate of 1.7mm/ year.
The rate increased to 3.2mm/year between 1993-2010.
Global mean sea level will continue to rise through the 21^st century at an ever increasing rate, due to increased ocean warming and melting of glaciers and ice sheets.

The Environment Agency in Britain has recently developed the Thames Estuary 2100 plan to manage the future flood threat to London. The motivation was a fear that due to accelerated sea level rise as the climate changed it might already be too late to replace the Thames Barrier (completed in 1982) and other measures that protect London, because such major engineering schemes take 25 to 30 years to plan and implement.

Ocean Circulation

As the temperature and precipitation at high latitudes increase over the 21st century, it is very likely that the Atlantic Meridional Overturning Circulation and its individual components (such as the North Atlantic Drift) will weaken but it is very unlikely that it will undergo an abrupt transition or collapse.

Ocean Acidification

Anthropogenic CO₂emissions cause the oceans to absorb more CO₂, which increases the acidity of the water. The pH of surface seawater has decreased by 0.1 since the beginning of the industrial era. By the end of the 21^st century, the additional decrease in surface ocean pH is projected to be in the range of 0.06 – 0.32. The consequences of changes in pH for marine organisms and ecosystems are just beginning to be understood.

Rocky shores are one of the few ecosystems for which field evidence of the effects of ocean acidification is available. The community structure of a site in the NE Pacific shifted from a mussel to an algal-barnacle dominated community between 2000 and 2008, as the pH declined rapidly.

The effect on marine ecosystems and coastal economies.

Rapid changes in the physical and chemical conditions within ocean sub-regions have already affected the distribution and abundance of marine organisms and ecosystems. As the oceans warm, marine organisms are moving to higher latitudes to maintain a constant temperature, with fish and zooplankton migrating at the fastest rates.
Changes to sea temperature have also altered the phenology or timing of key life-history events such as plankton blooms, and migratory patterns and spawning in fish and invertebrates.
30 years of temperature increase, have been partly responsible for boosting high latitude fisheries in the North Pacific and North Atlantic.
Climate change will result in more frequent extreme weather events and greater associated risks to ocean ecosystems.
Projected changes pose significant uncertainties and risks to fisheries, aquaculture and other coastal activities. In some cases (e.g. mass coral bleaching and mortality), projected increases will eliminate ecosystems, increase risks to food security and the vulnerability of coastal communities.
Climate related risks to the sustainability of capture fisheries and aquaculture, adding to the threats of over-fishing and other non-climate stressors. Shifts in the distribution and abundance of large pelagic fish stocks will have the potential to create ‘winners’ and ‘losers’ among island nations and economies.

Practical adaptation options(e.g. strengthening buildings and coastal defences, expanding areas of coastal vegetation) and supporting international policies (e.g. cooperative efforts to regulate fisheries, managing shared river systems to avoid erosion) can minimize the risks and maximize the opportunities.

IPCC links

This is SPM figure 9 from the WG1 report for the 2013 IPCC 5AR.

WG1 Figure SPM.7 shows ocean pH

AR4 Box TS.4 Sea Level

WG1 FAQ 3.2 Is there evidence for changes in the Earth’s water cycle?

WG1 FAQ 5.2 How unusual is the current sea level rate of change?

WG1 FAQ 13.1 Why does local sea level change differ from the global average?

WG1 FAQ 3.3 How does anthropogenic ocean acidification relate to climate change?

WGII FAQ 5.1 How does climate change affect coastal marine ecosystems?

WGII FAQ 6.3 Why are some marine organisms affected by ocean acidification?

WGII FAQ 6.4 What changes in marine ecosystems are likely because of climate change?

WGII FAQ5.3 How can coastal communities plan for and adapt to the impacts of climate change, in particular sea level rise?

8) Extreme Weather Hazards

Impact of Climate and Weather

People and ecosystems across the world experience climate in many different ways. Average climate conditions give a starting point for understanding what grows where, tourist destinations and other business opportunities.

However, changes in average (climate) conditions are often closely linked to changes in the frequency, intensity or duration of extreme weather events. Extreme weather places excessive and often unexpected demands on systems unable to cope and leads to losses and disruption. For example;

wet conditions lead to flooding when storm drains and other infrastructure for handling excess water are overwhelmed;
buildings fail when wind speeds exceed design standards;
drought can cause crop failure;
heat waves can cause sickness and death.

Changes in Extreme Weather

There is strong evidence that warming has led to changes in temperature extremes – including heat waves – since the mid-20^th century. In some locations, the occurrence of heat waves has more than doubled due to human influence.

Increases in heavy precipitation have probably also occurred over this time, but vary by region. It is likely that the number of heavy precipitation events over land has increased in more regions than it has decreased in since the mid-20^th century. In North America and Europe, the frequency or intensity of heavy precipitation events has probably increased.

In the Near East, India and central North America modern large floods are probably comparable to or surpass historical, pre-industrial floods in magnitude and/or frequency.

In some other regions (including northern and central Europe), historical floods were larger than those recorded since 1900.

mekong river — Image reproduced from the UNEP Vital Water Graphics report.

There is less certainty about other extremes, such as tropical cyclones, due to a lack of historical data. In the North Atlantic, tropical cyclone numbers and intensity have increased but it cannot yet be said whether these are related to climate change or not. In the future, it is likely that the global frequency of tropical cyclones will decrease or stay the same, although maximum wind speeds and rainfall will increase.

There has been a poleward shift and intensification of the mid-latitude depressions in the North Atlantic from the 1950s to the early 2000s, which is linked to a poleward shift in Northern Hemisphere jet streams.

IPCC links

This is FAQ 2.2 figure 2 from the WG1 report for the 2013 IPCC 5AR.

WG1 FAQ 2.2 Have There Been Any Changes in Climate Extremes?

WGII FAQ 1 Are risks of climate change mostly due to changes in extremes, changes in average climate, or both?

WG1 TFE.9 table 1 Global scale assessment of recent extreme weather and climate events

From 4AR: Box TS.5 Extreme Weather Events

9) The Impact of Climate Change on Food Production

Negative impacts of climate change on crop yields have been more common than positive impacts (some positive trends are evident in some high latitude regions).
Climate change has negatively affected wheat and maize yields for many individual regions and globally since 1960. The effects on rice and soybean yield have been smaller in major production regions and globally, with particularly few studies available of soy.
The majority of the impact has been on food production, however food access, utilization, and price stability could be affected. In recent years, several periods of rapid food and cereal price increases following climate extremes in key producing regions indicate a sensitivity of current markets to climate extremes.
There is a large negative sensitivity of crop yields to extreme daytime temperatures at around 30°C. Temperature trends are therefore important for determining both past and future impacts of climate change on crop yields at sub-continental to global scales.
Local temperature increases in excess of about 1°C above pre-industrial are projected to have negative effects on yields for the major crops (wheat, rice and maize) in both tropical and temperate regions, although individual locations may benefit. It is more difficult to predict the future effect of changes in local precipitation, and the interactions between CO₂ and mean temperature, extremes, water and nitrogen.

IPCC links

This is Figure SPM Figure 2c from the WGII report for the 2014 IPCC 5AR.

WGII FAQ7.1 What factors determine food security and does low food production necessarily lead to food insecurity?

WGII FAQ7.3 How could adaptation actions enhance food security and nutrition?

WGII Figure 7.3 History of FAO food and cereal price index showing the impact of extreme weather events on world food prices

CCAFS report: Climate change, food security and small-scale producers: Summary of findings of the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change (IPCC)

10)The Impact of Climate Change on Security

Human security will be progressively threatened as the climate changes. Human insecurity almost never has single causes, however climate change is an important factor through;

a) increasing migration that people would rather have avoided,

b) undermining livelihoods,

c) challenging the ability of states to provide the conditions necessary for human security,

d) compromising cultural values that are important for community and individual wellbeing.

Migration and mobility are ways people adapt to climate variability in all regions of the world. In the past, major extreme weather events have led to significant population displacement, and changes in the incidence of extreme events will amplify the challenges and risks of such displacement. However, many vulnerable groups, particularly in rural and urban areas in low and middle-income countries, do not have the resources to be able to migrate to avoid the impacts of floods, storms and droughts. Migration may be undesirable, and can lead to changes in important cultural expressions and practices, and, in the absence of institutions to manage the settlement and integration of migrants in destination areas, can increase the risk of poverty, discrimination, violent conflict and inadequate provision of public services, public health and education.

Future challenges of climate change:

A) Physical impacts: Sea level rise, extreme events and hydrological disruptions, pose major challenges to vital transport, water, and energy infrastructure and can weaken states socially and economically.

B) Territorial impacts: For example those highly vulnerable to sea level rise.

C) Transboundary impacts: Changes in sea ice, shared water resources, and the migration of fish stocks, have the potential to increase rivalry among states.

D) Violent conflict can in turn undermine livelihoods, impel migration and weaken valued cultural expressions and practices.

E) Adaptation and mitigation strategies, such as those which develop large infrastructure or the resettle communities against their will to reduce exposure to climate change, carry risks of disrupted livelihoods, displaced populations, deterioration of valued cultural expressions and practices, and in some cases violent conflict.

In summary, climate change is one of many risks to the vital core of material well-being and culturally specific elements of human security that varies depending on location and circumstance.

On the basis of current evidence about the observed impacts of climate change on environmental conditions, climate change will be an increasingly important cause of human insecurity globally in the future. The greater the impact of climate change, the harder it is to adapt.

IPCC links

This is Figure 12.3 from the WGII report for the 2014 IPCC 5AR.

WGII FAQ 12.1: What are the principal threats to human security from climate change?

WGII FAQ 12.3: How many people could be displaced as a result of climate change?

WGII FAQ12.4: What role does migration play in adaptation to climate change, particularly in vulnerable regions?

WGII FAQ 12.5: Will climate change cause war between countries?

GLOSSARY

Aerosols A suspension of airborne solid or liquid particles, with a typical size between a few nanometres and 10 μm that reside in the atmosphere for at least several hours.

Anthropogenic Resulting from or produced by human activities.

Atlantic Meridional Overturning Circulation A major current in the Atlantic Ocean, characterized by a northward flow of warm, salty water in the upper layers of the Atlantic, and a southward flow of colder water in the deep Atlantic. It includes the North Atlantic Drift and the Gulf Stream.

Attribution The process of evaluating the relative contributions of multiple causal factors to a change or event with an assignment of statistical confidence

Climate The average weather, or more rigorously, the statistical description in terms of the mean and variability of relevant quantities over a period of time ranging from months to thousands or millions of years. The classical period for averaging these variables is 30 years, as defined by the World Meteorological Organization. The relevant quantities are most often surface variables such as temperature, precipitation and wind.

Climate Change A change in the state of the climate that can be identified (e.g. by using statistical tests) by changes in the mean and/or the variability of its properties, and that persists for an extended period, typically decades or longer. Climate change may be due to natural internal processes or external forcings such as modulations of the solar cycles, volcanic eruptions, and persistent anthropogenic changes in the composition of the atmosphere or in land use.

Climate Model A numerical representation of the climate system based on the physical, chemical and biological properties of its components, their interactions and feedback processes, and accounting for some of its known properties. Climate models are applied as a research tool to study and simulate the climate, and for operational purposes, including monthly, seasonal and interannual climate predictions.

Cryosphere All regions on and beneath the surface of the Earth and ocean where water is in solid form, including sea ice, lake ice, river ice, snow cover, glaciers and ice sheets, and frozen ground (which includes permafrost).

Drought A period of abnormally dry weather long enough to cause a serious hydrological imbalance. Drought is a relative term; therefore any discussion in terms of precipitation deficit must refer to the particular precipitation-related activity that is under discussion.

Feedback An interaction in which a perturbation in one climate quantity causes a change in a second, and the change in the second quantity ultimately leads to an additional change in the first. A negative feedback is one in which the initial perturbation is weakened by the changes it causes; a positive feedback is one in which the initial perturbation is enhanced.

Forcings Forcing represents any external factor that influences global climate by heating or cooling the planet. Examples of forcings are volcanic eruptions, solar and orbital variations and anthropogenic (human) changes to the composition of the atmosphere.

Greenhouse Gas Those gaseous constituents of the atmosphere, both natural and anthropogenic, that absorb and emit radiation at specific wavelengths within the spectrum of terrestrial radiation emitted by the Earth’s surface, the atmosphere itself, and by clouds.

Hadley Cell A direct, thermally driven overturning cell in the atmosphere consisting of poleward flow in the upper troposphere, subsiding air into the subtropical anticyclones, return flow as part of the trade winds near the surface, and with rising air near the equator in the so-called Intertropical Convergence Zone.

Internal variability Variations in the mean state and other statistics (such as the occurrence of extremes) of the climate on all spatial and temporal scales beyond that of individual weather events, due to natural unforced processes within the climate system because, in a system of components with very different response times and complex dependencies, the components are never in equilibrium and are constantly varying. An example of internal variability is El Niño, a warming cycle in the Pacific Ocean which has a big impact on the global climate, resulting from the interaction between atmosphere and ocean in the tropical Pacific.

Inter-Tropical Convergence Zone The Inter-Tropical Convergence Zone is an equatorial zonal belt of low pressure, strong convection and heavy precipitation near the equator where the northeast trade winds meet the southeast trade winds. This band moves seasonally.

Paleoclimate Climate during periods prior to the development of measuring instruments, including historic and geologic time, for which only proxy climate records are available.

Pelagic Any water in a sea or lake that is neither close to the bottom nor near the shore.

Phenology The study of periodic plant and animal life cycle events and how these are influenced by seasonal and interannual variations in climate, as well as habitat factors.

Mitigation A human intervention to reduce the amount of climate change for example by reducing the sources or enhance the sinks of greenhouse gases.

Reconstruction Approach to reconstructing the past temporal and spatial characteristics of a climate variable from predictors. The predictors can be instrumental data if the reconstruction is used to infill missing data or proxy data if it is an indirect measure used to develop paleoclimate reconstructions.

Stratosphere The highly stratified region of the atmosphere above the troposphere extending from about 10 km (ranging from 9 km at high latitudes to 16 km in the tropics on average) to about 50 km altitude.

Troposphere The lowest part of the atmosphere, from the surface to about 10 km in altitude at mid-latitudes (ranging from 9 km at high latitudes to 16 km in the tropics on average), where clouds and weather phenomena occur. In the troposphere, temperatures generally decrease with height.

Uncertainty A state of incomplete knowledge that can result from a lack of information or from disagreement about what is known or even knowable. It may have many types of sources, from imprecision in the data to ambiguously defined concepts or terminology, or uncertain projections of human behaviour.

UK National Curriculum Links

KS3 geography

Physical geography relating to: weather and climate, including the change in climate from the Ice Age to the present.
Understand how human and physical processes interact to influence, and change landscapes, environments and the climate; and how human activity relies on effective functioning of natural systems.

GCSE Geography

Changing weather and climate – The causes, consequences of and responses to extreme weather conditions and natural weather hazards, recognising their changing distribution in time and space and drawing on an understanding of the global circulation of the atmosphere. The spatial and temporal characteristics, of climatic change and evidence for different causes, including human activity, from the beginning of the Quaternary period (2.6 million years ago) to the present day.

What is the UK’s Climate Like?

Post date 9 November 2020

The United Kingdom spans latitudes of 50 to 62°C N. It has a maritime climate with four distinct seasons.
Average annual temperature varies between 4.5 °C in winter to 14 °C in summer with warmer conditions in the South.
Rainfall is highest in autumn and winter; average of approximately 110 mm per month, and 75 mm per month in spring and summer.
Mean annual rainfall varies between 2500mm in mountainous areas such as Wales to 500mm in the drier region of East Anglia.
Year to year variations in climate are linked to the North Atlantic Oscillation (NAO) which causes shifts in the average track of storms.

UK Climate – Current and Future

Post date 9 November 2020

UK

IPCC 2013 Figures

Post date 8 November 2020

Trends in the frequency (or intensity) of various climate extremes (arrow direction denotes the sign of the change) since the middle of the 20th century (except for North Atlantic tropical cyclones where the period covered is from the 1970s).

Some Figures and Tables from the IPCC 2013 Fifth Assessment Report

WG1 – The Physical Science Basis

WG2- Impacts, Adaptation and Vulnerability

IPCC, 2014: Climate Change 2014: Impacts, Adaptation, and Vulnerability. Working Group II Contribution to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

What is a hurricane?

The Great Storm of 1987

The storm gathers

Warning the public

How the storm measured up

A hurricane or not?

The aftermath

Floods and flooding

The devastation floods can cause

Flooding caused by surges

The surge of 1953

Storm tide warnings

Surges still causing damage

Flood defences

Floods Devastate Village

Physical Impacts

Responses to the flooding

In Pictures

What happened to cause this event?

Weather chart

A snowy day in Winter 2005

Impacts

What happened to cause this weather?

Climate Change Updates

What is the key evidence for climate change?

Why is the cryosphere so important?

Is recent climate change similar to anything that has happened in the past?

What is Forcing?

IPCC links

3) Causes of Recent Changes in Global Surface Temperature

IPCC links

4) The Earth’s Energy Balance

How do human activities affect the Earths energy budget?

IPCC links

5) Changes to the Global Atmospheric Circulation

How might precipitation change?

How does cloud height affect climate?

What is the outlook?

IPCC links

6) Impacts of Climate Change Already Observed

IPCC links

7) Sea level and marine ecosystems

Sea Level

Ocean Circulation

Ocean Acidification

The effect on marine ecosystems and coastal economies.

IPCC links

8) Extreme Weather Hazards

Impact of Climate and Weather

Changes in Extreme Weather

IPCC links

9) The Impact of Climate Change on Food Production

IPCC links

10)The Impact of Climate Change on Security

Future challenges of climate change:

IPCC links

GLOSSARY

UK National Curriculum Links

KS3 geography

GCSE Geography

UK

WG1 – The Physical Science Basis

WG2- Impacts, Adaptation and Vulnerability

WG3 – Mitigation of Climate Change

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